Fuel preheating system

ABSTRACT

The present invention provides fuel saving systems. Fuel consumption can be reduced by 5% to 40% or more by pre-combustion heating the fuels. The heat exhaust of a combustion chamber can be used to heat a heat transfer fluid, which exchanges heat with the incoming fuel stream.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.12/645,428, filed Dec. 22, 2009, which claims the benefit of TurkishPatent Application 2008/09852 filed on Dec. 26, 2008, which applicationsare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Industrial and consumer applications commonly use fossil fuels to createenergy. Fossil fuel derived gases can be referred to as natural gas,which comprises a gas consisting primarily of methane. It is foundassociated with fossil fuels, in coal beds, as methane clathrates, andis created by methanogenic organisms in marshes, bogs, and landfills. Itis an important fuel source, a major feedstock for fertilizers, and apotent greenhouse gas.

Natural gas is a major source of electricity generation through the useof gas turbines and steam turbines. Most grid peaking power plants andsome off-grid engine-generators use natural gas. Particularly highefficiencies can be achieved through combining gas turbines with a steamturbine in combined cycle mode. Natural gas burns more cleanly thanother fossil fuels, such as oil and coal, and produces less carbondioxide per unit energy released. For an equivalent amount of heat,burning natural gas produces about 30% less carbon dioxide than burningpetroleum and about 45% less than burning coal. Combined cycle powergeneration using natural gas is thus the cleanest source of poweravailable using fossil fuels, and this technology is widely usedwherever gas can be obtained at a reasonable cost.

At the current state of the technology, natural gas is transferred toits final destination of use in gas form by means of pipes or pressureresistant tankers or in liquid form again in pressure resistant tankers.Gases that are transferred under high pressure by means of pipes ortankers from their production points are reduced in pressure at pressurereducing stations and then delivered to the end user. Valves andsecurity equipment are used in order to ensure the security of thestations and impede the back charge of the gas.

Extraction, production and transportation from long distances by meansof pipes or pressure resistant tankers are a costly process. In manysystems, the gas delivered to the end user by pipes enters into thecombustion chamber at the delivery temperature, which can vary accordingto geography, season, transfer method and storage location.

The present invention provides fuel savings and enhanced efficiency ofmany kinds of combustible fuels, including without limitation naturalgas, liquefied petroleum gas (LPG), Liquefied natural gas (LNG),compressed natural gas (CNG), cold compressed natural gas (CCNG), etc.Fuel consumption can be reduced by 5% to 40% or more by pre-combustionheating of the fuels.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a system comprising: aheating chamber configured and arranged to heat a fuel; a combustionchamber fluidly connected to the heating chamber, wherein the combustionchamber is configured and arranged to receive the fuel heated in theheating chamber and to combust the fuel therein; and a heat exchangeelement, wherein the heat exchange element is configured to transferexhaust heat generated by the combustion chamber to the heating chamber.

In some embodiments, the system is constructed and arranged such thatexhaust heat is transferred to the heating chamber using a heat transferfluid. In some embodiments, the heating chamber comprises: an inlet forthe heat transfer fluid; a pipe constructed and arranged to transportthe heat transfer fluid; an outlet for the heat transfer fluid; and afuel flow pipe constructed and arranged to allow heat exchange betweenthe fuel and the heat transfer fluid. The heating chamber can comprise anumber of shapes, including without limitation a cylindrical, triangularprism, or rectangular prism shape. In some embodiments, the heattransfer fluid flows through a spiral heating pipe inside the heatingchamber. The fuel flow pipe may have internal baffles, e.g., to provideturbulent flow to more evenly heat the fuel flowing therein.

In some embodiments, the system is configured and arranged such that aportion of the fuel is not preheated before entering the combustionchamber. In some embodiments, the systems of the invention furthercomprise an exhaust chimney in fluidic communication with the combustionchamber. The temperature inside the exhaust chimney can be monitored.These configurations can be used to control the temperature of the fuelentering combustion chamber to an optimal level.

In some embodiments, the systems of the invention further a pool systemconstructed and arranged to reduce the flow of the heat transfer fluidto the heating chamber. For example, the heat transfer fluid can bediverted to the pool system to reduce its flow. The pool system can beengaged to reduce the flow of the heat transfer fluid to the heatingchamber when the fuel supply decreases or when the temperature of thefuel entering the combustion chamber exceeds the desired level.

The system of the invention can also comprise a transfer apparatus toprovide positive force to circulate the heat transfer fluid. Suchapparatus can comprise pumps, valves, and combinations thereof.

In another aspect, the present invention provides a system comprising:a) a heating chamber configured and arranged to heat a fuel, wherein theheating chamber comprises: i) an inlet for a heat transfer fluid; ii) apipe constructed and arranged to transport the heat transfer fluid; iii)an outlet for the heat transfer fluid; and iv) a fuel flow pipeconstructed and arranged to allow heat exchange between the fuel and theheat transfer fluid, wherein the fuel flow pipe optionally comprisesinternal baffles; b) a combustion chamber fluidly connected to theheating chamber, wherein the combustion chamber is configured andarranged to receive the fuel heated in the heating chamber and tocombust the fuel therein; c) a heat exchange element, wherein the heatexchange element is configured to transfer exhaust heat generated by thecombustion chamber exhaust to the heating chamber using the heattransfer fluid; d) a transfer apparatus to provide positive force tocirculate the heat transfer fluid; and e) optionally comprising a poolsystem constructed and arranged to reduce the flow of the heat transferfluid to the heating chamber when the fuel supply decreases or when thetemperature of the fuel entering the combustion chamber exceeds thedesired level. In some embodiments, the heat transfer fluid comprises amineral oil of formula C₁₂H₂₆—C₁₆H₃₄ and the fuel comprises natural gas,liquefied petroleum gas (LPG), liquefied natural gas (LNG), orcompressed natural gas (CNG).

In any of the systems of the invention, the heat transfer fluid maycomprise a gas phase. In some embodiments, the gas phase heat transferfluid comprises air, hydrogen, inert gases, helium, nitrogen, carbondioxide, sulfur hexafluoride, steam or a combination thereof.

In any of the systems of the invention, the heat transfer fluid maycomprise a liquid phase. In some embodiments, the liquid phase heattransfer fluid comprises water, highly pure deionized water, heavywater, antifreeze, ethylene glycol, diethylene glycol, or propyleneglycol, betaine, polyalkylene glycol, oil, mineral oil, castor oil,silicone oil, fluorocarbon oil, transformer oil, nanofluids or acombination thereof. In some embodiments, the heat transfer fluidcomprises a mineral oil, e.g., a paraffin mineral oil of formulaC₁₂H₂₆—C₁₆C₃₄.

The fuel entering the systems of the invention may comprise a liquidfuel, a gas fuel, or a combination thereof. In some embodiments, thefuel entering the systems comprises a gasoline, jet fuel, natural gas,liquefied petroleum gas (LPG), liquefied natural gas (LNG), compressednatural gas (CNG), naphtha, propane, diesel, heating oil, kerosene, fueloil, distillate fuel oil, diesel fuel oil, light fuel oil, residual fueloil, heavy fuel oil, gasoil, bunker fuel, alcohol fuel, E85, ethanolfuel, ethanol fuel mixtures, biodiesel, biogas, or a combinationthereof. In some embodiments, the fuel comprises natural gas, liquefiedpetroleum gas (LPG), liquefied natural gas (LNG), or compressed naturalgas (CNG).

The systems of the invention can be configured and arranged to beretrofit to a preexisting fuel burning system. The systems can also beincorporated into a novel fuel burning system.

Some embodiments of the systems of the invention comprise a valve toregulate the pressure of the fuel and/or impede a back flow of the fuel.Some embodiments also comprise a pressure reducing station, wherein thepressure reducing station is configured to reduce the pressure of thefuel before the fuel enters the heating chamber. Some embodimentscomprise a volume increasing station, wherein the volume increasingstation is configured to increase the volume of the fuel before the fuelenters the heating chamber. Such arrangements may be used, e.g., toexpand a liquid fuel to a gas phase, e.g., a liquid natural gas tonatural gas.

In any of the systems of the invention, the systems can be constructedand arranged such that at least a portion of a combustion air ispreheated before entering the combustion chamber. In addition, the fuelmay be heated by an additional heat source.

In some embodiments, the systems of the invention comprise one or moreof a Britalus rotary engine, Coomber rotary engine, free-piston engine,gas turbine, aeroderivative, turbojet, jet engine, auxiliary power unit,industrial gas turbine, turboshaft engine, radial gas turbine,micro-jet, microturbine, external combustion engine, rotary turbine,internal combustion engine, Internally Radiating Impulse Structure(Iris) engine, turbofan engine, rocket engine, ramjet engine, Mintowheel, orbital engine, Sarich orbital engine, reciprocating engine,piston engine, quasiturbine engine (Quirbines), pistonless rotaryengine, rotary combustion engine, RotationsKolbenMaschinen (RKM) engine,Trochilic engine, Engineair engine, Rand cam engine, Atkinson cycleengine, liquid-piston engine, Gerotor engine, split-single engine(twingles), steam engine, reciprocating steam engine, beam engine,stationary steam engine, boiler, multiple expansion engine, uniflowengine, steam turbine, noncondensing turbine, backpressure turbine,condensing turbine, reheat turbine, extracting turbine, Stirling engine,swing-piston engine, oscillating piston engine, vibratory engine,toroidal engine, Tschudi engine, and a Wankel engine. The invention canbe used to provide fuel savings with these or other fuel burningengines.

In some embodiments, the systems of the invention are constructed andarranged such that the fuel is heated in the heating chamber by at leastabout 1° C., 2° C., 3° C., 4° C., 5° C., 6° C., 7° C., 8° C., 9° C., 10°C., 12° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50°C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 90° C., 95° C., 100°C., 110° C., 120° C., 125° C., 130° C., 140° C., 150° C., 160° C., 170°C., 175° C., 180° C., 190° C., 200° C., 225° C., 250° C., 275° C., 300°C., 325° C., 350° C., 375° C., 400° C., 425° C., 450° C., 475° C., 500°C., 525° C., 550° C., 575° C., 600° C., 625° C., 650° C., 675° C., 700°C., 725° C., 750° C., 775° C., 800° C., 825° C., 850° C., 875° C., 900°C., 925° C., 950° C., 975° C., or at least about 1000° C. The optimalfuel preheating can be determined for each deployed system.

In some embodiments, the systems of the invention are constructed andarranged such that the fuel is heated in the heating chamber so that itenters the combustion chamber at about 1° C., 2° C., 3° C., 4° C., 5°C., 6° C., 7° C., 8° C., 9° C., 10° C., 12° C., 15° C., 20° C., 25° C.,30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C.,75° C., 80° C., 90° C., 95° C., 100° C., 110° C., 120° C., 125° C., 130°C., 140° C., 150° C., 160° C., 170° C., 175° C., 180° C., 190° C., 200°C., 225° C., 250° C., 275° C., 300° C., 325° C., 350° C., 375° C., 400°C., 425° C., 450° C., 475° C., 500° C., 525° C., 550° C., 575° C., 600°C., 625° C., 650° C., 675° C., 700° C., 725° C., 750° C., 775° C., 800°C., 825° C., 850° C., 875° C., 900° C., 925° C., 950° C., 975° C., orabout 1000° C. The optimal fuel preheating can be determined for eachdeployed system.

In some embodiments, the systems of the invention are constructed andarranged such that the increased fuel efficiency provided by the systemare at least about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%,20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%,95%, 100%, 110%, 120%, 125%, 130%, 140%, 150%, 160%, 170%, 175% , 180%,190%, 200%, 225%, 250%, 275%, 300%, 325%, 350%, 375%, 400%, 425%, 450%,475%, 500%, 525%, 550%, 575%, 600%, 625%, 650%, 675%, 700%, 725%, 750%,775%, 800%, 825%, 850%, 875%, 900%, 925%, 950%, 975%, or at least about1000%.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 illustrates a system view used in the implementation of theinvention.

FIG. 2 illustrates a perspective view of the heating chamber parts usedin an implementation of the invention.

FIG. 3 illustrates another system view used in the implementation of theinvention.

FIG. 4 illustrates a system view implemented with an alternative heatsource.

FIG. 5 illustrates an alternative gas flow device.

FIG. 6 illustrates fuel savings versus temperature using a Riello RS 300800/M BLU Series Low NOx Modulating Gas Burners. The Y-axis shows theinput temperature of the preheated natural gas to the burner. The X-axisshows the fuel saving realized.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides fuel savings. The systems of theinvention preheat fuels prior to combustion, thereby increasing fuelefficiency and reducing consumption. The components of the system aremounted prior to the combustion chamber. For fuels that are expanded,e.g., natural gas, the components can be mounted after the pressuredecreasing station. The systems of the invention can be retrofit topreexisting fuel systems without damaging the infrastructure. Forexample, the systems can be retrofit to preexisting turbine engines, gasengines, internal combustion engines, external combustion engines,boilers and the like. In other embodiments, the invention isincorporated into energy producing systems at the design stage.

According to Charles' law, also known as the law of volumes, gases tendto expand when heated. The law states that at constant pressure, thevolume of a given mass of an ideal gas increases or decreases by thesame factor as its temperature on the absolute temperature scale (i.e.the gas expands as the temperature increases). The coefficient ofexpansion is about the same for all the common gases at ordinarytemperatures; it is 1/273 of the volume at 0° C. per degree rise intemperature. Conversely, when a gas is heated while maintaining thevolume, the pressure increases. The systems of the invention takeadvantage of these principles by preheating the fuel prior to combustionto improve fuel efficiency. Whereas preheating combustion air canconcomitantly increase noxious emissions, preheating the fuel input maynot increase such emissions and may lower the emissions, e.g., byreducing the amount of fuel burned.

The present invention provides fuel saving and enhanced efficiency ofmany kinds of gas fuels, including without limitation natural gas,liquefied petroleum gas (LPG), Liquefied natural gas (LNG), compressednatural gas (CNG), cold compressed natural gas (CCNG), etc. Theprinciples of the system can also be applied to systems using oil orother fuels and petroleum products, e.g., light oil, light oil/naturalgas, heavy oil, diesel, gasoline or other fuel burning systems. Theprinciples can be applied in a variety of industrial and personalsettings, e.g., to steam boilers, turbines, home appliances, householdtype boilers and the like. Various types of fuel burning heat engine cantake advantage of the systems of the invention. Such engines includewithout limitation Britalus rotary engines, Coomber rotary engines,free-piston engines, gas turbines, aeroderivatives, turbojets, jetengines, auxiliary power units, industrial gas turbines, turboshaftengines, radial gas turbines, micro-jets, microturbines, externalcombustion engines, rotary turbines, internal combustion engines,Internally Radiating Impulse Structure (Iris) engines, turbofan engines,rocket engines, ramjet engines, Minto wheels, orbital engines, Sarichorbital engines, reciprocating engines, piston engines, quasiturbineengines (Quirbines), pistonless rotary engines, rotary combustionengines, RotationsKolbenMaschinen (RKM) engines, Trochilic engines,Engineair engines, Rand cam engines, Atkinson cycle engines,liquid-piston engines, Gerotor engines, split-single engines (twingles),steam engines, reciprocating steam engines, beam engines, stationarysteam engine, boilers, multiple expansion engines, uniflow engines,steam turbine, noncondensing turbines, backpressure turbines, condensingturbines, reheat turbines, extracting turbines, Stirling engines,swing-piston engines, oscillating piston engines, vibratory engines,toroidal engines, Tschudi engines, and Wankel engines. One of skill inthe art will appreciate that the systems can be used in any appropriatesetting wherein a fuel is subjected to combustion. The efficiency gainswill depend on each particular system.

Commercial fuels that can be used with the systems of the inventioninclude without limitation gasoline, jet fuel, natural gas, naphtha,propane, diesel, heating oil, kerosene, fuel oils, distillate fuel oils,diesel fuel oils, light fuel oils, residual fuel oils, heavy fuel oils,gasoil, bunker fuel, and renewable fuels such as alcohol fuel, E85,ethanol fuel and mixtures thereof, biodiesel and biogas.

Liquefied natural gas (LNG) is natural gas that has been convertedtemporarily to liquid form for ease of storage or transport. Liquefiednatural gas takes up about 1/600th the volume of natural gas in thegaseous state. The natural gas is purified of certain impurities thencondensed into a liquid at close to atmospheric pressure by cooling toapproximately −162° C. LNG is principally used for transporting naturalgas to markets, where it is regasified and distributed as pipelinenatural gas.

Compressed natural gas (CNG) is made by compressing natural gas, to lessthan 1% of its volume at standard atmospheric pressure. It is stored anddistributed in hard containers, at a normal pressure of 200-220 bar(2900-3200 psi), usually in cylindrical or spherical shapes. CNG is usedin traditional gasoline internal combustion engine cars that have beenconverted into bi-fuel vehicles (gasoline/CNG).

Liquefied petroleum gas (LPG) is a mixture of hydrocarbon gases used asa fuel in heating appliances and vehicles. LPG includes mixes that areprimarily propane, mixes that are primarily butane, and mixes includingboth propane and butane. Propylene and butylenes can also be present insmall concentration. LPG is synthesized by refining petroleum or ‘wet’natural gas, and is usually derived from fossil fuel sources. It can bemanufactured during the refining of crude oil, or extracted from oil orgas streams as they emerge from the ground. LPG is supplied inpressurized steel containers.

In some embodiments, the systems of the invention heat the fuel inheating chamber. Any appropriate heating methods may be used. Theseinclude without limitation electrical energy, solar energy, hot steam,hot liquid, or combinations thereof.

In one embodiment, the heat provided to the incoming gas is recycledfrom the exhaust heat or flue gas of the combustion chamber. Forexample, the incoming fuel or a portion thereof, can absorb heat througha heat exchange with the exhaust gas. Fuels can be mixed or combinedwith an oxygen source prior to combustion. A common source of combustionair is atmospheric air. In some embodiments, some or all of thecombustion air is also preheated prior to combustion using the same ordifferent source of heat than the preheated fuel.

The fuel savings produced by the system can be dependent on thetemperature to which the fuel is heated prior to combustion. Controlsystems can be used so that the fuel is heated to a particulartemperature for each application. For example, when the fuel reaches acertain preheated temperature, the heat exchange can be reduced by anynumber of methods. For example, a portion of the fuel can be diverted sothat it does not enter the heat exchanger. Or the flow rate or volume ofhot air or liquid in the heat exchanger can be reduced. When natural gasor other fuels are expanded prior to combustion, the temperature of thegas can drop with the reduction in pressure. In these cases, the fuelcan be preheated prior to or after the expansion step, or both beforeand after expansion.

The fuel can be preheated before combustion by about 1° C., 2° C., 3°C., 4° C., 5° C., 6° C., 7° C., 8° C., 9° C., 10° C., 12° C., 15° C.,20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C.,65° C., 70° C., 75° C., 80° C., 90° C., 95° C., 100° C., 110° C., 120°C., 125° C., 130° C., 140° C., 150° C., 160° C., 170° C., 175° C., 180°C., 190° C., 200° C., 225° C., 250° C., 275° C., 300° C., 325° C., 350°C., 375° C., 400° C., 425° C., 450° C., 475° C., 500° C., 525° C., 550°C., 575° C., 600° C., 625° C., 650° C., 675° C., 700° C., 725° C., 750°C., 775° C., 800° C., 825° C., 850° C., 875° C., 900° C., 925° C., 950°C., 975° C., or about 1000° C. In some embodiments, the fuel ispreheated by more than about 1000° C.

The fuel can be preheated before combustion to about 5° C., 10° C., 15°C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60°C., 65° C., 70° C., 75° C., 80° C., 90° C., 95° C., 100° C., 110° C.,120° C., 125° C., 130° C., 140° C., 150° C., 160° C., 170° C., 175° C.,180° C., 190° C., 200° C., 225° C., 250° C., 275° C., 300° C., 325° C.,350° C., 375° C., 400° C., 425° C., 450° C., 475° C., 500° C., 525° C.,550° C., 575° C., 600° C., 625° C., 650° C., 675° C., 700° C., 725° C.,750° C., 775° C., 800° C., 825° C., 850° C., 875° C., 900° C., 925° C.,950° C., 975° C., or 1000° C. In some embodiments, the fuel is preheatedby more than 1000° C.

In one embodiment, the invention preheats the fuel and/or combustion airprior to combustion by using heat exchange with the hot flue gas. Anumber of types of heat exchangers can be used in the systems of theinvention. These include without limitation shell and tube heatexchangers, plate heat exchangers, regenerative heat exchangers,recuperative heat exchangers, adiabatic wheel heat exchangers, plate finheat exchangers, fluid heat exchangers, waste heat recovery units,dynamic scraped surface heat exchanger, phase-change heat exchangers,spiral heat exchangers, or a combination thereof. The fuel andcombustion air can be preheated using different or the same type ofexchanger. In some embodiments, the fuel and combustion air, or aportion of either, are premixed then preheated prior to combustion. Insome embodiment, the heat exchanger is a direct heat exchanger. Directcontact heat exchangers involve heat transfer between hot and coldstreams of two phases in the absence of a separating wall.

In some embodiments, the heat exchange is via an indirect heatexchanger. FIG. 1 depicts an exemplary embodiment of the inventionwherein the fuel is preheated by passing a heat transfer fluid throughthe flue exhaust to absorb heat. Heat from the hot heat transfer fluidis then exchanged with the fuel in heating chamber 5.

As shown in FIG. 2, heating chamber 5 comprises of a bottom part 2 and atop part 3. Seal 21 serves to prevent leaks. Gas fuel flow pipe 1 withat least one entrance 7 and at least one exit 8 passes from pressurereducing or volume expanding station 18 through heating chamber 5.Heating chamber components 2 and 3 are mounted together with bolts 4 andthe heating chamber 5 is mounted on the gas flow pipe 1 by completelycovering it at the selected section. These two sections allow heatingchamber 5 to be retrofit to a preexisting system. Heating chamber 5 canbe configured to have different sizes and shapes depending on theparticular system. For example, when the system is used in a retrofitdesign, heating chamber 5 can be configured and adapted for thepreexisting piping carrying the fuel to the combustion chamber. In someembodiments, heating chamber 5 comprises a cylindrical shape,rectangular prism, triangular prism, or has varying shapes along itslength. Any appropriate shape can be used given the energy producingsystem at hand. The fluid inlet 6 typically resides on the top ofheating chamber 5. Before the system starts operation, heating chamber 5can be filled with the heat transfer fluid at fluid inlet 6. Theaddition of the heat transfer fluid to the system can be a onetimeoperation and can be performed right after the system installation andbefore the first running of the system. Before the combustion chamber isstarted, the heat transfer fluid can be cool, e.g., at room temperature,or can be preheated using an external heat source (electrical, thermal,solar, etc).

The heat transfer fluid exits heating chamber 5 from fluid drain 9 andpasses through heat transfer fluid pipe 10. The heat transfer fluid hasreduced temperature at drain 9 relative to its temperature at inlet 6due to heat exchange with the cooler fuel. Heat transfer fluid pipe 10can be constructed of copper or other appropriate piping material. Theheating fluid travels through heat transfer fluid pipe 10 where itreaches the exhaust chimney 11 to be reheated by heat exchange with theflue gas. The temperature at exhaust chimney 11 depends on theconditions of the fuel combustion system and can range from, e.g., 100°C. to 300° C. and above. In some embodiments, the temperature is above100° C., 110° C., 120° C., 125° C., 130° C., 140° C., 150° C., 160° C.,170° C., 175° C., 180° C., 190° C., 200° C., 225° C., 250° C., 275° C.,300° C., 325° C., 350° C., 375° C., 400° C., 425° C., 450° C., 475° C.,500° C., 525° C., 550° C., 575° C., 600° C., 625° C., 650° C., 675° C.,700° C., 725° C., 750° C., 775° C., 800° C., 825° C., 850° C., 875° C.,900° C., 925° C., 950° C., 975° C., 1000° C., 1500° C., 2000° C., 2500°C. or above about 3000° C. In some embodiments, heat transfer fluid pipe10 is positioned directly within the chimney 11. As shown in the figure,this section of transfer pipe 10 can be spiral shaped to increase theheating surface and thereby allow the heat transfer fluid which entersexhaust chimney 11 to absorb more heat. Hot fluid exiting the exhaustchimney 11 travels through heat transfer fluid pipe 10 and entersheating chamber 5 through fluid inlet 12. Valve 13 at the heated fluidinlet can be used to release pressure and air as necessary.

Heat is transferred in heating chamber 5 from the heat transfer fluid tothe fuel flowing in a countercurrent arrangement through fuel pipe 1. Insome embodiments, the system can be constructed and arranged so that theheat transfer fluid and fuel flow in a concurrent arrangement. Duringthis heat transfer, the fuel flowing through the fuel pipe 1 is heatedas it traverses heating chamber 5. Conversely, the heat transfer fluidis cooled during the heat transfer as it heats the fuel flowing throughfuel pipe 1. The heat transfer fluid flows back into heat transfer fluidpipe 10 after passing through fluid drain 9 at bottom part 2. The heattransfer fluid repeats the above procedure with a continuous cycle,thereby continuously heating the fuel flowing through fuel pipe 1towards the combustion chamber. Transfer apparatus 15 can be comprisedof pumps and the like to provide a positive flow of the heat transferfluid through the system.

In some embodiments, pool system 14 is used. Pool system 14 can be putinto operation when fuel flow into the system is interrupted or when thetemperature of the heat transfer fluid exiting exhaust chimney 11exceeds the desired value for the system at hand. In this manner, thesystem can prevent overheating the fuel before it enters the combustionchamber. Various components can be used to measure the temperature ofthe heat transfer fluid exiting from within exhaust chimney 11. In oneembodiment, the temperature of the exhaust chimney 11 is measured bythermometer 19 placed inside the chimney 11. In another embodiment, thetemperature of the heat transfer fluid itself is measured. Multipletemperature measurements can be made at various points of the system asdesired. If the temperature of the exhaust flue gas and/or heat transferfluid leaving exhaust chimney 11 falls below and/or rises above thedesired temperature, the valve on transfer apparatus 15 positioned ontransfer pipe 10 can be closed so that the flow of the heat transferfluid is reduced, thereby reducing the amount of heat carried by theheat transfer fluid entering heating chamber 5.

When the fuel flow is interrupted, pool system 14 can stop the heatingsystem from functioning and prevent the remaining fuel in fuel pipe 1from being heated. In another embodiment, transfer apparatus 15 cantransfer the heat transfer fluid in heat transfer fluid pipe 10 toexhaust chimney 11. One of skill in the art will appreciate thattransfer apparatus 15 can be comprised of pumps and valves asappropriate.

FIG. 3 depicts another exemplary implementation of the subject systemwherein heating chamber 5 completely surrounds fuel pipe 1 in one piece.Fuel pipe 1 extends out from both ends of heating chamber 5. Heatingchamber 5 can be mounted into the system by disconnecting or cutting outa portion of the fuel pipe 1, e.g., as it exits the pressure decreasingstation before reaching the combustion chamber. Heating chamber 5 ismounted by reconnecting fuel pipe 10, e.g. by welding at section 20.

FIG. 3 further shows an alternate arrangement for the heat transferfluid pipe as it traverses heating chamber 5. In this configuration, aspiral heating pipe which contains the heat transfer liquid is woundaround fuel pipe 1 within heating chamber 5. One end 17 of this woundsection of pipe is connected to the heat transfer fluid intake 12 andthe other is connected to the heat transfer fluid drain 9. In thisimplementation, the fluid in the spiral pipe transfers heat to theincoming fuel. Furthermore, valve 16 can be implemented to regulate thepressure so that it does not exceed the system's mechanical-strength andto impede backflow.

FIG. 4 shows another exemplary embodiment of the above invention whereinan alternate source of heat 22 is used to heat the heat transfer fluidbefore it enters the spiral heating pipe 23 and thereafter the heatingchamber 5. This configuration can be used in place of the systemdescribed above or along side. In one embodiment, the alternate heatsource 22 is used to heat the heat transfer fluid when the system isfirst started up. The alternate energy source can comprise anyappropriate system that can supply energy, e.g., an electric source,thermal source, solar source, energy supplied from another combustionsystem operating nearby, or the like. As the exhaust temperature reachesa sufficient level, the system can begin to recycle heat from theexhaust chimney 11. The alternate energy source can then be turned offif appropriate. The alternate energy source can also be configured andadapted to supply additional heat if the temperature of the heattransfer fluid becomes too low to sufficiently preheat the fuel enteringthe combustion chamber.

In another exemplary embodiment, shown in FIG. 5, an alternativeconfiguration is used for the fuel pipe. The internal baffles in thepipe section 26 facilitate mixing of the fuel as it flows through pipe,thereby facilitating even heating of the fuel stream. Entrance 24 andexit 25 comprise conical body connections. The structures can also bemicrostructures placed with fuel pipe 1 as shown above.

A variety of fluids can be used as the heat transfer fluid of theinvention. In some embodiments, the heat transfer fluid can be heatedand used for heat transfer up to the desired input temperature of thefuel into the combustion chamber. The fluids can also be chosen tomaintain operable form and flow characteristics up to their boilingpoints. The fluid can comprise a gas, e.g., air or steam, or comprise aliquid, e.g., water or oil. In some embodiments, the heat transfer fluidis maintained in one phase as it circulates through the system. In someembodiments, the heat transfer fluid undergoes a phase shift as it isheated and cooled. In a non-limiting example, the heat transfer fluidcould comprise liquid water, steam, or a combination thereof. Forexample, the fluid may consist essentially of a gas phase as it exitsheated from exhaust chimney 11 but comprise a liquid as it exits cooledfrom heating chamber 5.

Gases that can be used to transfer heat include without limitation air,hydrogen, inert gases, helium, nitrogen, carbon dioxide, sulfurhexafluoride and steam. Liquids that can be used to transfer heatinclude without limitation water, highly pure deionized water, heavywater, antifreeze (e.g., water carrying an organic chemical such asethylene glycol, diethylene glycol, or propylene glycol), betaine,polyalkylene glycol and oils. Oils are often used when water is notsuitable, e.g., at temperatures above the boiling point of water (i.e.,100° C. at atmospheric pressure). Appropriate oils include withoutlimitation mineral oils, castor oil, silicone oil, fluorocarbon oils,and transformer oil. These oils often have high boiling points and canbe used in industrial processes. Nanofluids, e.g., fluids such as thoseabove containing nanoparticle additives, can also be used.

In some embodiments, the heat transfer liquids used in the exemplaryimplementations herein comprise oil. In some embodiments, the oilscomprise mineral oil. Mineral oil or liquid petroleum is a by-product inthe distillation of petroleum to produce gasoline and other petroleumbased products from crude oil. It is a transparent, colorless oiltypically comprised of alkanes (typically 15 to 40 carbons) and cyclicparaffins. Three basic classes of refined mineral oils include: 1)paraffinic oils, based on n-alkanes; 2) naphthenic oils, based oncycloalkanes; and 3) aromatic oils, based on aromatic hydrocarbons.

In some embodiments, the heat transfer oil comprises paraffin oil withgeneral formula: CH₂—CH₂—CH₂—CH₂ . . . In some embodiments, the carbonchain comprises between C₁₂ and C₄₀, e.g., between C₁₂ and C₁₆. Thelatter paraffin oils are described by the formula C₁₂H₂₆—C₁₆H₃₄.

The fuel savings provided by the system will depend on the type of fuel,type of combustion chamber, feasibility of retrofitting a fuel burningsystem, available heat to supply to the fuel, and numerous otherfactors. In some embodiments, the systems can achieve fuel savings of atleast about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 20%, 25%,30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, or at leastabout 95%. The reduction in fuel usage to produce the same amount ofenergy can be at least about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%,12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%,80%, or at least about 90%. In some embodiments, the reduction in fuelusage is at least about 90%.

One of skill will appreciate that other methods can be combined with thesystems of the invention to provide further increases in fuelefficiency. For example, as noted herein, some or all of the combustionair entering the combustion chamber can be preheated. Heat from theexhaust or an additional heat source could be used to heat thecombustion air. In some embodiments, the combustion air and fuel aremixed and then heated before entering the combustion chamber. Thecombustion air heating may however lead to increased noxious emissionsfrom the exhaust. In addition, adjustments to the air/fuel ratioentering the burner, e.g., by increasing the air/fuel ratio, can provideadditional fuel savings. In some embodiments, increasing the air/fuelratio can provide at least about a 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%,10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%,75%, 80%, 90%, 95%, or 100% additional increase in fuel efficiency. Insome embodiments, it was observed that the fuel savings provided by theinvention increased with the molecular weight of a gas fuel. That is ifhigher molecular weight gases are burned even high percentage of savingsare obtained.

FIG. 6 shows results obtained by implementing a preheating system of theinvention to retrofit a Riello RS 300 800/M BLU Series Low NOxModulating Gas Burners system. Natural gas feed to the burner waspreheated using heat reclaimed from the exhaust chimney using a liquidheat transfer oil comprising C₁₂H₂₆—C₁₆H₃₄. The system was constructedand arranged as described herein. As shown in FIG. 6, fuel savings ofabout 40% were realized as the input temperature of the fuel into theburner was increased from 30° C. to 200° C. During these experiments, itwas further observed that the time to produce a certain energy out ofthe system decreased significantly, which resulted in the fasterproduction of steam.

One of skill in the art will appreciate that the various components ofthe system can be constructed and arranged to suit a variety ofdifferent scenarios. For example, the heating chamber can be constructedand arranged to adapt to retrofit a preexisting energy producing system.Various embodiments of the heating chamber are described herein andthese and other designs can be adapted as appropriate. Similarly, themanner in which the heat transfer fluid exchanges heat with the exhaustcan be depend on the particular system. In some embodiments, heattransfer fluid pipe 10 is placed directly within the exhaust flue. Inother embodiments, heat is exchanged indirectly with the exhaust. One ofskill will appreciate that the modular design of the system lends itselfto these and other modifications.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A system for combusting fuel, comprising: (a) apressure reducing station that reduces the pressure of a fuel directedinto said pressure reducing station; (b) a heating chamber separatefrom, downstream of, and fluidically connected to the pressure reducingstation, wherein said heating chamber is configured to receive said fuelfrom said pressure reducing station and heat said fuel with the aid ofelectrical energy; and (c) a combustion chamber fluidically connected tosaid heating chamber, wherein said combustion chamber is configured andarranged to receive said fuel heated in said heating chamber and tocombust said fuel therein.
 2. The system of claim 1, further comprisinga heat exchange element, wherein said heat exchange element isconfigured and arranged to transfer heat to the heating chamber.
 3. Thesystem of claim 2, wherein said system is constructed and arranged suchthat heat is generated with the aid of said electrical energy and istransferred to said heating chamber using a heat transfer fluid.
 4. Thesystem of claim 3, wherein said heating chamber comprises: (a) an inletand an outlet for said heat transfer fluid; (b) a pipe constructed andarranged to transport said heat transfer fluid from said inlet to saidoutlet; and (c) a fuel flow pipe constructed and arranged to allow heatexchange between said fuel and said heat transfer fluid.
 5. The systemof claim 4, wherein said fuel flow pipe is circumscribed in whole orpart by said pipe.
 6. The system of claim 3, wherein said heat transferfluid comprises a gas phase heat transfer fluid.
 7. The system of claim6, wherein said gas phase heat transfer fluid comprises air, hydrogen,inert gases, helium, nitrogen, carbon dioxide, sulfur hexafluoride,steam or a combination thereof.
 8. The system of claim 3, wherein saidheat transfer fluid comprises a liquid phase heat transfer fluid.
 9. Thesystem of claim 8, wherein said liquid phase heat transfer fluidcomprises water, highly pure deionized water, heavy water, antifreeze,ethylene glycol, diethylene glycol, or propylene glycol, betaine,polyalkylene glycol, oil, a paraffin oil of formula C₁₂H₂₆—C₁₆H₃₄,napthenic oil, aromatic oil, mineral oil, castor oil, silicone oil,fluorocarbon oil, transformer oil, nanofluids or a combination thereof.10. The system of claim 1, wherein said system is configured andarranged such that a portion of said fuel is not preheated beforeentering said combustion chamber.
 11. The system of claim 1, whereinsaid fuel comprises gasoline, jet fuel, natural gas, liquefied petroleumgas (LPG), liquefied natural gas (LNG), compressed natural gas (CNG),naphtha, propane, diesel, heating oil, kerosene, fuel oil, distillatefuel oil, diesel fuel oil, light fuel oil, residual fuel oil, heavy fueloil, gasoil, bunker fuel, alcohol fuel, E85, ethanol fuel, ethanol fuelmixtures, biodiesel, biogas, or a combination thereof.
 12. The system ofclaim 1, wherein, in said pressure reducing station, a liquid fuel isvaporized to a gaseous fuel.
 13. The system of claim 1, wherein saidsystem is configured and arranged to be retrofitted to a preexistingfuel burning system.
 14. A method for combusting fuel, comprising: (a)directing a fuel into a pressure reducing station, wherein said pressurereducing station reduces the pressure of said fuel; (b) directing thefuel from the pressure reducing station to a heating chamber separatefrom, downstream of, and fluidically connected to said pressure reducingstation, wherein said heating chamber heats said fuel; and (c) directingsaid fuel from said heating chamber to a combustion chamber, whereinsaid fuel is combusted in said combustion chamber.
 15. The method ofclaim 14, wherein heat generated from said combustion is transferred tosaid heating chamber to heat said fuel.
 16. The method of claim 14,wherein, in said pressure reducing station, a liquid fuel is vaporizedto a gaseous fuel.
 17. The method of claim 14, wherein said heatingchamber heats said fuel with the aid of electrical energy.
 18. Themethod of claim 14, wherein said fuel is combusted in said combustionchamber using combustion air.
 19. The method of claim 18, wherein atleast a portion of said combustion air is preheated before entering saidcombustion chamber.
 20. The method of claim 18, wherein said combustionair is fed into said combustion chamber separate from said fuel.
 21. Themethod of claim 14, wherein said fuel is not mixed with combustion airprior to exiting said heating chamber.
 22. The method of claim 14,wherein a fuel savings provided by said method is at least 5%.
 23. Themethod of claim 14, wherein said fuel comprises gasoline, jet fuel,natural gas, liquefied petroleum gas (LPG), liquefied natural gas (LNG),compressed natural gas (CNG), naphtha, propane, diesel, heating oil,kerosene, fuel oil, distillate fuel oil, diesel fuel oil, light fueloil, residual fuel oil, heavy fuel oil, gasoil, bunker fuel, alcoholfuel, E85, ethanol fuel, ethanol fuel mixtures, biodiesel, biogas, or acombination thereof.